A. Field of the Invention
The present invention generally relates to temperature control systems and methods, and, more particularly, to a new and improved self-cleaning oven temperature control system and method utilizing multiple, redundant oven temperature sensing elements.
B. Description of the Prior Art
Self-cleaning ovens and temperature controls therefor are old and well known in the prior art as exemplified by U.S. Pat. Nos. 3,121,158; 3,122,626; 3,310,654; 3,327,094; 3,353,004; 3,569,670; 3,648,012; 3,738,174; 3,924,101; 4,166,268; 4,214,224; and 4,369,352. Conventionally, the bake temperature controls for many prior art self-cleaning ovens are capable of being recalibrated in service to compensate for oven components that deviate from design specifications or to accommodate individual user preferences. See, for example, the above-identified '670 patent and the '101 patent and the '352 patent. Some prior art temperature control systems for self-cleaning ovens are designed to maintain a constant clean temperature even though the bake temperatures have been recalibrated and offset by a predetermined amount from nominal value. Recalibration of the bake temperatures in order prior art systems necessarily affects the clean temperature.
Modern electric ranges having self-cleaning ovens utilize digital electronic microprocessor based control systems for controlling the oven temperatures. Typically, such ovens include a conventional oven temperature sensor, for example, a temperature sensing probe, disposed in a protective housing in the oven cavity for sensing the oven temperature and for providing an output signal to the microprocessor of the control system for use in controlling the energization of the oven heating elements and, thereby, the temperature of the oven cavity. Therefore, the oven temperature sensor is a critical item in controlling the oven temperature.
Conventionally, when such an oven temperature sensor in an electronically controlled electric range has failed in either an electrically open condition or an electrically shorted condition, either such condition could be and has been detected electronically; and the oven of the range could be and has been safely shut down. However, a conventional oven temperature sensor may also experience a non-catastrophic failure. Specifically, the sensor may drift out of calibration in a manner that could cause the oven temperature to exceed its maximum allowable value requiring it to be shut down immediately for servicing. Therefore, a need exists to detect a variation or degradation in the performance of a conventional oven temperature sensor that is short of a catastrophic failure.